Method for assembling an epicyclic gear train

ABSTRACT

A method is disclosed of assembling an epicyclic gear train comprising providing a carrier that includes spaced apart walls and circumferentially spaced mounts interconnecting the walls in a one-piece unitary structure. Spaced apart apertures are provided between the mounts at an outer circumference of the carrier. Gear pockets are provided between the walls and mounts extending to the apertures, and a central opening is provided in at least one of the walls. An intermediate gear is inserted through the central opening. The intermediate gear moves radially into the gear pocket to extend through the aperture. A baffle is inserted into the carrier in a space between the walls. A sun gear is inserted through the central opening to intermesh with the intermediate gear.

This application is a divisional application of U.S. patent applicationSer. No. 11/481,112, which was filed on Jul. 5, 2006 now U.S. Pat. No.7,704,178.

BACKGROUND OF THE INVENTION

This invention relates to an oil baffle arrangement for use in anepicyclic gear train employed to drive a turbo fan.

Gas turbine engines typically employ an epicyclic gear train connectedto a turbine section of the engine, which is used to drive the turbofan. In a typical epicyclic gear train, a sun gear receives rotationalinput from a turbine shaft through a compressor shaft. A carriersupports intermediate gears that surround and mesh with the sun gear. Aring gear surrounds and meshes with the intermediate gears. Inarrangements in which the carrier is fixed against rotation, theintermediate gears are referred to as “star” gears and the ring gear iscoupled to an output shaft that supports the turbo fan. In arrangementsin which the ring gear is fixed against rotation, the intermediate gearsare referred to as “planetary” gears and the carrier is coupled to theoutput shaft that supports the turbo fan.

The epicyclic gear train gears must receive adequate lubrication duringoperation of the turbine engine. To this end, the carrier includes oilspray bars arranged between the intermediate gears and the sun gear tospray oil directly on those gears. Separate oil baffles, which may beintegral with or separate from the carrier, are arranged between theintermediate gears to collect the sprayed oil and retain it in the areaof the intermediate gears for prolonged lubrication before the oil iscollected in a lubricant gutter associated with the ring gear.

Prior art carrier arrangements have required multiple components andcomplicated assembly in order to accommodate the oil baffles. Forexample, one or both of the side walls of the carrier must be assembledaround the intermediate gears resulting in a multi-piece carrier.Furthermore, separate oil spray bars and oil baffles complicate assemblyand increase cost. What is needed is a simplified oil baffle and spraybar arrangement that enables a simpler and less expensive carrierdesign.

SUMMARY OF THE INVENTION

A turbine engine includes a epicyclic gear train that drives a turbofan. A carrier provides a unitary structure having spaced apart wallsinterconnected by circumferentially spaced mounts providingcircumferentially spaced apertures at an outer circumference of thecarrier. The carrier supports intermediate gears that surround and meshwith a centrally located sun gear. The intermediate gears extend throughthe apertures to mesh with a ring gear that surrounds the carrier.Baffles are arranged between the side walls adjacent to the mounts.Fasteners secure the baffles, which can be a different material than thecarrier, to the carrier. The baffles include a lubrication passage thatdistributes oil to various parts of the epicyclic gear train.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a front portion of a gasturbine engine illustrating a turbo fan, epicyclic gear train and acompressor section.

FIG. 2 is a cross-sectional view of the epicyclic gear train shown inFIG. 1.

FIG. 3 is an end view of the epicyclic gear train taken along line 3-3in FIG. 2 with a pair of star gears shown in phantom in an installationposition.

FIG. 4 is an enlarged view of a portion of the epicyclic gear trainshown in FIG. 3 with a sun gear and star gears shown in phantom.

FIG. 5 is an enlarged view of a portion of the epicyclic gear trainshown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A portion of a gas turbine engine 10 is shown schematically in FIG. 1.The turbine engine 10 includes a fixed housing 12 that is constructedfrom numerous pieces secured to one another. A compressor section 14having compressor hubs 16 with blades are driven by a turbine shaft (notshown) about an axis A. A turbo fan 18 is supported on a turbo fan shaft20 that is driven by a compressor shaft 24, which supports thecompressor hubs 16, through an epicyclic gear train 22.

In the example arrangement shown, the epicyclic gear train 22 is a stargear train. Of course, the claimed invention also applies to otherepicyclic gear trains such as a planetary arrangement. Referring to FIG.2, the epicyclic gear train 22 includes a sun gear 28 that is connectedto the compressor shaft 24, which provides rotational input, by asplined connection 30. A carrier 34 is fixed to the housing 12 by atorque frame 36. The carrier 34 supports intermediate gears (which arestar gears 32 in the arrangement shown) that are coupled to the sun gear28 by meshed interfaces 26 between the teeth of the sun and star gears28, 32. A ring gear 38 surrounds the carrier 34 and is coupled to thestar gears 32 by meshed interfaces 44. The ring gear 38, which providesrotational output, is secured to the turbo fan shaft 20 by connection42.

In one example, the torque frame 36 grounds the carrier 34 to thehousing 12 in a known manner. For example, mounts 53 have apertures 56receiving fingers of the torque frame 36, as shown in FIGS. 2 and 3.Pins 48 that extend through spherical bearings 46 and bushings 52 securethe fingers to the carrier 34. Fasteners 50 retain the pins 48 to thecarrier 34.

The carrier 34 is a unitary structure manufactured from one piece forimproved structural rigidity and ease of assembly. The carrier 34includes spaced apart side walls 60 that are interconnected by themounts 54, which are generally wedge-shaped members, as best shown inFIG. 3. The mounts 54 and side walls 60 are unitary with one another.The mounts 54 have opposing curved surfaces 58 that are in closeproximity to the star gears 32 and generally follow the curvature of theteeth of the star gears 32 so that any oil on the curved surfaces 58will likely find its way to the star gears 32 for additionallubrication.

The mounts 54 are circumferentially spaced about the carrier 34 toprovide apertures 98 through which the star gears 32 extend to engagethe ring gear 38. Returning to FIG. 2, the side walls 60 include holes62 for receiving a journal bearing 64 that supports each of the stargears 32. Each journal bearing 64 is retained within the carrier 34 byretainers 66 fastened to the side walls 60.

Oil baffles 68 are arranged between the side walls 60 near each of themounts 54, best shown in FIG. 2. Referring to FIGS. 4 and 5, the baffles68 include ends 72 that abut the mounts 54, in the example shown. Thebaffles 68 also include opposing curved surfaces 70 arranged in closeproximity to the star gears 28. The curved surfaces 58, 70 arecontiguous with and adjoin one another, in the example shown, andprovide gear pockets 102 that receive the star gears 32. A gear pocket104, which receives the sun gear 28, is also provided between a surface73 on each of the baffles 68 opposite the ends 72.

In one example, one of the side walls 60 includes holes 74 that receivefasteners 76 which secure each of the baffles 68 to the carrier 34. Thebaffles 68 include a lubrication passage provided by a primary passage86 that fluidly communicates with a lubricant distributor 78. Thelubricant distributor 78 is fed oil from a lubricant supply 96. In oneexample, the baffles 68 include openings 82 that receive a tube 80extending through a hole 83 in the side wall 60. Seals 84 seal the tube80 to the opening 82 and lubricant distributor 78. Other tubes 92 havingseals 84 are used to provide oil to an external spray bar 94 throughanother lubrication passage (spray bar passage 93 that extends throughone of the baffles 68). The external spray bar 94 is secured to thecarrier 34 and sprays oil in the vicinity of the sun gear 28 near thesplined connection 30 (shown in FIGS. 2 and 5).

The primary passage 86 is in communication with first and secondpassages 88, 90 that spray oil on the teeth of the sun and star gears28, 32. In the example shown, the first and second passages 88, 90 arearranged ninety degrees from one another.

With the example baffles 68, lubricant distribution is integrated intothe baffle so that separate components are eliminated. The baffles 68can be constructed from a different, lighter weight material than thecarrier 34.

The example carrier 34 can be constructed from one piece, which improvesthe structural integrity of the carrier. A central opening 100 ismachined in at least one of the side walls 60 and provides the gearpocket 104. Gear pockets 102 are machined between the side walls 60 andmounts 54 for each of the star gears 32 and form apertures 98 at anouter circumference of the carrier 34. Referring to FIG. 3, the stargears 32 are inserted into the central opening 100 and moved radiallyoutwardly so that they extend through the apertures 98 and arepreferably in abutment with the mounts 54 (position indicated by dashedlines in FIG. 3). In this position, there is an adequate gap, t, betweenthe teeth of adjacent star gears 32 to accommodate a width, w, of theend 72 of the baffles 68. Once the baffles 68 have been inserted, thestar gears 32 can be repositioned, as shown by the solid lines, and thesun gear 28 can be inserted into the central opening 100 so that itmeshes with the star gears 32. The baffles 68 are secured to the carrier34 using fasteners 76. The tubes 80, 92 can be inserted and the rest ofthe lubricant distribution system can be connected.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

1. A method of assembling an epicyclic gear train comprising the stepsof: a) providing a carrier that includes spaced apart walls andcircumferentially spaced mounts interconnecting the walls in a one-pieceunitary structure, spaced apart apertures provided between the mounts atan outer circumference of the carrier, gear pockets provided between thewalls and mounts extending to the apertures, and a central opening in atleast one of the walls; b) inserting an intermediate gear through thecentral opening; c) moving the intermediate gear radially into the gearpocket to extend through the aperture; d) inserting a baffle into thecarrier in a space between the walls subsequent to performing steps a)and b); and e) inserting a sun gear through the central opening tointermesh with the intermediate gear.
 2. The method according to claim1, wherein step d) includes securing the baffle to the carrier near theintermediate gear.
 3. The method according to claim 2, wherein step d)includes bolting the baffle to one of the walls.
 4. The method accordingto claim 1, comprising inserting a tube through a hole in the carrier tocommunicate with a lubrication passage in the baffle.
 5. The methodaccording to claim 1, comprising securing a torque frame to the mounts,the torque frame fixed relative to a housing.